Rom. Astron. J., Vol. 18, Supplement, p. 000–000, Bucharest, 2008 INVESTIGATION OF A POLAR FILAMENT ERUPTION IN STAGES CRISTIANA DUMITRACHE, IULIA CHIFU, MARILENA MIERLA Astronomical Institute of the Romanian Academy Str. Cuţitul de Argint 5, 040557 Bucharest, Romania E-mail: crisd@aira.astro.ro Abstract. A huge polar filament erupted on 8 January 2002 giving rise to three CMEs observed by SOHO. We analyze the dynamics of this filament in order to detect the mechanism that produced its destabilization. The filament erupted in several phases. Few active regions were observed at the South end of the filament. We study the extrapolated 3D coronal magnetic field evolution of zone, in order to understand the influences of these active regions on the filament dynamics. We also focus on the CMEs evolution from the solar disk to the interplanetary space. Key words: Sun – filaments – CME – data analysis. 1. INTRODUCTION Solar filaments are dense and cold plasma features suspended in the hot solar corona. They are sustained against the gravity by the magnetic field. Prominences and filament channels form along the photospheric polarity inversion lines and by that they are really tracers of solar magnetic field. Often small prominences merge into larger ones, continuous structures on timescales of a few days (Malherbe 1989). Several authors reported observations on merging filaments (van Ballegooijen 2004; Schmieder et al. 2004): this phenomenon seems to be possible when they have the same chirality or sign of magnetic helicity. Aulanier et al. (2006) simulated the prominence merging process and found responsible for that a mechanism consisting of a complex coupling between photospheric shear, coronal magnetic reconnections without null points, and formation of quasi-bald patches. Very often the filaments erupt in coronal mass ejections (CME) and for that reason they have importance in space weather study as solar sources of CMEs. Destabilizations and eruptions of filaments are associated with photospheric activity, and CMEs onsets constitute manifestations of the relaxation of large-scale highly stressed solar magnetic fields. The places of filaments apparition on the solar disk change during the solar